The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A conventional hydraulic damper or shock absorber comprises a cylinder which is adapted at one end for attachment to the sprung or unsprung mass of a vehicle. A piston is slidably disposed within the cylinder with the piston separating the interior of the cylinder into two fluid chambers. A piston rod is connected to the piston and extends out of one end of the cylinder where it is adapted for attachment to the other of the sprung or unsprung mass of the vehicle. A first valving system is optionally incorporated within the piston as a safety hydraulic relief valve which functions during the shock absorber's extension stroke of the piston with respect to the cylinder and a second valving system is incorporated within the piston for allowing fluid replenishment above the piston during the shock absorber's compression stroke of the piston with respect to the cylinder.
Various types of adjustment mechanisms have been developed to generate damping forces in relation to the speed and/or amplitude of the displacement of the sprung or unsprung mass. Often, the damping characteristics are controlled by an externally mounted control valve. An externally mounted control valve is advantageous in that it may be easily removed for service or replacement.